If you want a 6 channel amp that'll actuall deliver all it's rated power into each channel, it'll cost you. Bryston make theirs with a seperate power transformer for each channel. Some others probably do too, but that's the only one I know of. I have researched many multichannel amps, so I'm not too sure who makes what other than Bryston.
If the sonic improvement is worth the expense is a personal thing; depends on ears and wallet.
If the sonic improvement is worth the expense is a personal thing; depends on ears and wallet.